An element whose presence turns many gemstones green and yet a few red.
Chromium is a steely grey metal that can be found as a chemical element in the periodic table and although jewellery is rarely made of it, it does have an important role to play in gemstones.
Many gemstones are allochromatic: this means that their colour is derived from small traces of elements or impurities not included in the chemical composition of the gem. Chromium is the main red colouring agent in Corundum and turns the mineral into the precious Ruby.
However, in gems such as Tsavorite Garnet and Emerald, its presence is the reason why we get such vibrantly vivid greens.
And, as if by magic, its presence in some Chrysoberyl is what provides it with its ability to colour change from green or bluish-green in daylight, to a soft shade of red, purplish-red or raspberry red in artificial light (incandescent light). When this colour change is present in Chrysoberyl, we rename the gemstone Alexandrite.
Russian Diopside which is a very rare and truly beautiful green gemstone that is unearthed in inhospitable conditions in Siberia also receives its colour from chromium and in the gem trade the it is more often referred to as Chrome Diopside.
